Indicator circuits



United States Patent "a `2,922,149 INDICATOR CIRCUITS John Paul Jones, Jr., Pottstown, Pa., assigner to Navigatron Computer Corporation, a corporation of Pennsylvama Application May 21, 1956, serial Na. 585,996

4 Claims. (Cl. 340-252) i This invention relates in general to indicator circuits, and 1n particuluar to indicator circuits for indicating the electrical state of circuits characterized by relatively low voltage differentials such `as transistor circuits and the like.

Electronic computers and other systems may include Vcircuit indication means for providing a visual indication of the electrical state of circuits used therein. In the case'of such `systems using VVvacuum tubes, the indicating function is accomplished readily by connecting a neon lamp, for example. to an appropriate point in the circuit. The voltage changes or differential provided by the tube" as it b ecomes more or less conductive are relatively great, and amply suicient to operate the neon or glow discharge lamp. In the case of relatively low voltage circuits, however, such as electrical circuits using transistors, the changes in voltage at any point in the circuit are relatively low, making it impractical heretofore to use neon or glow discharge lamps as the indicating means. asis well known, voltage differentials of thirty volts or more between their tiring and quench potentials. In low voltage circuits, such as transistor'circuits, voltage differentials of ten volts are normal and the'differentials scldom exceed twenty volts. To provide some means for indicating the electrical state of such circuits', therefore, incandescent lamps of the filament type have been usd. It would be preferable, however, to use neon or gas discharge lamps in such circuits since incandescent lamps are low impedance devices and dissipate relatively large amounts of power.- Neon orglow discharge lamps, however, are'highy impedance devices and dissipate very little power. While possessing this advantage, neon lamps aresubject to long term drift in that the potentials needed for ring and lquenching the lamps may vary. This characteristic has also heretofore made the use of neon lamps impractical with relatively low voltage differential circuits. 2

It is, accordingly, an object of this invention to provide neon or glow discharge lamp indicator circuits for Vindicating Vthe electrical state of electrical circuits in which the voltage changes therein are relatively low.

lIt is anothere object of this invention to provide, in electrical circuits utilizing transistors, improved indication 'means including a neon or glow discharge lamp for indicating the electrical state of the circuits.

It is a further object of this invention to provide improved circuit means, including aneon or glow discharge lamp, for providing reliable and e'icient indication of the electrical state or condition of relatively low voltage circuits such as those using transistors.

It is yet another object of the present invention to provide improved means. including a neon or glow discharge lamp. for providing reliable indication of the electrical state of bistable circuits despite drift of the neon or glow discharge lamp used therein.

In accordance with the present invention, a neon or glow discharge lamp is connected in series between a Neon or glow discharge lamps may require,

2,922,149 lPatented Jam 19 1969 ICC . 2 relatively low voltage device or circuit, the electrical state of which is to be indicated, and a power supply source comprising a direct-current bias supply and alternating current source. An example of this type source wouldbe an unfiltered or poorly ltered direct-current powersupply. By using a power supply of this type, in which voltage variations of the alternating-current voltage may be of the order of twenty volts peak-to-peak, the required voltage differential for tiring and subse'- Iquently quenching the neon lamp is obtainable, irrespective of the fact that the device or circuit whose electrical state is `to be indicated provides relatively low voltage dilerentials. In the case of an electrical circuit utilizing transistors, therefore, the present invention makes it possible to indicate the electrical state of the circuit with a relatively low dissipation and reliable neon lamp.

The novel features that are considered characteristic of this invention areV set forth with particularity in the appended claims. The invention itself, however, both as toits organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing, in which:

Figure l is a circuit diagram, partially in block form, of an indicating circuit embodying the invention;

Figure 2 is a graph illustrating various voltages in a circuit of the type illustrated in Figures l, 3, and 4i -Figure'3 is a schematic circuit diagram of an indicating circuit embodying the invention used with a transistor bistable multivibrator circuit; and

Figure 4 is a schematic circuit diagram of an indicating circuit embodying the invention as used with a transis- -tor oscillator circuit.

Referring now to the drawing, wherein like parts are indicated by like reference numerals throughout the iigures,and referring in particular to Figure 1, an indicating system embodying the invention includes anvelectrical circuit or device 10, which will normally be of the type having two distinct electrical states. These states may bea state of low current conduction on the one hand,n and a state of high current conduction state on the other. Such a device or circuit is referred to as being bistable. These electrical states may simply be referred to as an on and an olf state. The device l0, as it changes from one state to another, will provide a voltage variation which will normally vary from be? tween 10 and 20 volts, for example. In other words, the device or circuit 10 is of the type in which the voltage differential between the on and off condition is relatively small. age differential would be insuicient to provide tiring and quenching of a neon lamp.

In accordance with the invention, a direct-current bias supply and alternating current source 12 is used and provides, in combination With the relatively small voltage differential of the electrical circuit or device 10, a suficient voltage variation or dilferential to fire a neon lamp 14. The lamp 14 and a current limiting resistor 16 are connected in series between the terminals of the electrical circuit 10 and the supply 12. The supply 12 could take any form inV which a direct-current supply voltage of for example 55 volts, and an alternatingcurrent voltage of, for example, 2 0 volts peak-to-peak is provided. An example of this type source would be an unfiltered or poorly filtered direct-current supply in which the ripple component provides the desired al- 4effectively provides reliable tiring and quenching of the neon lamp 1 4 to provide an indication of the electrical state of the electrical circuit 10 will be best understood Under ordinary circumstances, this voltfrom a consideration of the graph of Figure 2 wherein various typical voltages of a circuit of the type illustrated in Figure 1 are depicted. It will be assumed initially, at the time t1, that the Ycircuit of Figure l is conducting, that is, it is in the on condition 4or state. In this condition, it will be further assumed that the voltage at the output of the electrical circuit or device 10 is at ground potential or nearly at ground potential. The static voltage at the output circuit of the bias supply 12 is, meanwhile, maintained at a 55 'volt level, for example. Upon -this direct-voltage is superimposed an alternating current voltage or ripple voltage which has a peak-to-peak value of volts as shown by the simplified wave form 18. Accordingly the voltage 'differential across the neon bulb 14 in Figure 1 iluctuates between 45 and 65 volts as the ripple voltage 18 varies, and the neon lamp 14 will remain non-conductive.

At time t2, however, the electrical condition or state of the circuit 10 changes to a non-conducting or ott condition. This provides a negative square wave of voltage of for example, -20 volts as indicated by the voltage wave 20 of Figure 2. At some time during the non-conducting or off condition of the circuit 10, therefore, a voltage differential of 85 volts will be provided across the neon lamp 14 as indicated by the graph of Figure 2. This 85 volt differential is suicient to fire the neon lamp 14 which, therefore, lights or glows to give a visual indication of the non-conducting or off condition or state of the circuit 10. It is noted, moreover, that despite drift or other variations of the lamp 14, the voltage differential provided in accordance with the invention will be ample to insure ring of the lamp. At time t3, the circuit 10 is again in the' on or conducting condition and its output voltage is increased (i.e., becomes less negative) and is elTectively at zero or ground potential. Accordingly, the voltage `differential across the lamp 14 will vary between, 65 and 45 volts. normally a voltage differential of 50 volts or less is suicient to provide positive quench, the lamp 14 will be quenched when the ripple or alternating-current wave 18 passes through its negative cycle. Thus it is evident that by using a direct-current bias supply upon which an alternating-current voltage is superimposed, in accordance with the invention, positive tiring and quenching of a neon lamp is obtained even though the electrical'circuit with which it is associated provides a maximum voltage dilerential of 2() volts, such as has been assumed for the circuit 10 in Figure 1. At time t4, the circuit l'changes again to the off or non-conducting condition and the operation repeats as described to tire the neon lamp 14.

It is to be noted that the voltage values given are by way of example only. Since positive firing and quenching of a neon lamp is somewhat variable these voltage values may be altered within the scope of the invention depending on the particular circuit requirements. ln any event, positive and reliable indication of the electrical state of the low voltage differential circuit 10 is provided by utilizing a supply 12 of the type described.

One practical circuit application of the invention is illustrated in Figure 3 in which a bistable multivibrator circuit or ilip-tlop includes a pair of transistors 22 and 32 which may be considered to be junction transistors of the P-N-P type. The multivibrator circuit has been enclosed within the dotted rectangle 10 and is 'representative of the circuit whose electrical condition or state is to be indicated by the lamp 14. The transistors 22 and 32 include respective semi-conductive bodies 24 and 34, with which emitter electrodes 26 and 36, collector electrodes 28 and 38, and base electrodes 30 and 40, respectively, are cooperatively associated. The collector electrodes 30 and 40 are coupled through direct-current conductive load impedance elements, illustrated as a pair of resistors 42 and 44 respectively to the k,negative terminal of a suitable source of energizing potential, such as' a negative 20 voltV direct-current supply; for example,

Since The base 30 of the transistor 22 is coupled to the collector 38 of the transistor 32 through the parallel combination of a coupling resistor 46 and capacitor 48. The base 4t) of the transistor 32 is coupled to the collector 28 of the transistor 22 through the parallel combination of a coupling resistor 50 and` capacitor 52, thereby providing regenerative bistable operation. The emitter electrodes 26 and 36 are connected to a point of reference potential or circuit ground through a resistor 54. Input trigger signals from any convenient source may be applied to a pair of input terminals 56, one of which is grounded and the other of which is coupled in parallel to the base electrodes 30 and 40 through' a pair of isolating resistors 58 and 60. Successive input signals will trigger the bistable circuit 10 from an on or nonindicating state to an off or indicating state and viceversa.

The collector 38 of the transistor 32 is connected to the neon lamp 14. ,The other electrode of the neon lamp 14 is connected through the resistor 16 to, in accordance with the invention, the direct-current bias supply and alternating current s ource 12.

In operation, whenV the transistor 32 is in a condition of high current conduction, that is in the on condition, current ow in the collector 38 and through the load resistor 44 will provide a voltage drop thereacross which will make the collector voltage essentially zero, that is the ycollector 38 will be at substantially ground potential. Accordingly, the voltage differential across the neon lamp 14 (assuming voltage'values identical with those discussed relative to Figures 1 and 2) will vary between 45 and 65 volts which is insucient to fire the lamp. When the transistor 32 is in its non-conductive or off condition or state, however, essentially no collector current will flow and the voltage at the collector 38 will essentially be that of the negative supply, or a negative 20 volts at this time (the time t2 in Figure 2), and the voltage differential across the lamp 14 will be at least 65 volts and at some time during the non-conducting cycle will be volts. Accordingly, the lamp 14 will iire to give a positive indication of the non-conducting or off condition of the bistable circuit 10. When the transistor 38 becomes conductive again (at the time t4 in Figure 2), the voltage dilTerential across the lamp 14 will decrease to 45 volts which is sul'licie'ntv to quench the lamp 14, indicating that the circuit is in its on or conducting state.

The present invention is adaptable to practically any low voltage differential circuit having at least two distinct electrical states or conditions. In the circuit of Figure 4, for example,.the electrical circuit 10 is illustrated as being an oscillator having two stable states of operation, or an on and off state.` This circuit includes a transistor 62 which may be considered to be of the P-N-P junction type and which includes a semi-conductive body. 64, with which an emitter 66, a collector 68, and a base 70 are cooperatively associated. The collector 68 is connected through an inductive winding 72 and load resistor 74 to a negative source of direct-current supply voltage of, for example, -20 volts. The base 70 is connected to ground through a further inductive' winding 76 and a resistor 78 to ground. A resistor 80 is connected in parallel with the winding 76.V The inductive windings 72 and 76 are in inductive coupling relation to provide regenerative signal feedback between the collector 68 and base 70.

The emitter 66 of the transistor 62 is grounded through a stabilizing resistor 81. To provide on and off triggering of the oscillator circuit and thus two stable states or electrical conditions, the base 70 is connected through the resistor 78 and an isolating resistor 82 to a negative Vsource of trigger pulses, while the emitter 66 is coupled to a further suitable'source of negative trigger pulses through an isolating -resistor 84. The trigger pulses which nare applied tothe base will turn the oscillator circuit on,

while the trigger pulses which are applied to the emitter will turn the oscillator circuit oi.

The collector 68 is also connected through the inductive winding 72, the neon lamp 14 and the resistor 16 to, in accordance with the invention the direct-current bias supply and alternating-current source 12. The source 12 is again of the type which will provide a static voltage of 55 vol-ts, for example, upon which is superimposed an alternating voltage of, for example, 20 volts peak-topeak.

In operation, the circuit illustrated in Figure 4 is similar to the ones illustrated in Figures 1 and 3. In the state of high current conduction, that is in the oscillating or on condition, current -flow in the collector 68 and through the load resistor 74 will provide a voltage drop across the load resistor 74 which will make the voltage at the collector 68 essentially zero. The voltage differential across the neon lamp 14 will thus Vary, under the conditions assumed, between 45 and 65 volts. The neon lamp 14 will thus be extinguished. When the transistor 62 is in its oit or non-oscillating state, due to the application of a negative pulse to the emitter 66, essentially no collector current will ow and the voltage at the collector 68 will essentially be that of the supply or 20 Volts negative. The voltage differential across the neon lamp 1-4 will thus be at least 65 volts and a maximum of 85 volts. Accordingly, the lamp 14 will re to give a reliable indication of the non-conducting, non-oscillating or o condition of the oscillator circuit 10. The cycle then repeats and thek lamp 14 Will alternately become conductive and non-conductive.

As described, circuits embodying the invention provide positive and reliable means Afor indicating the electrical state of electrical circuits exhibiting low voltage diieren tials. Thus, indicating circuits in accordance with the invention provide a novel means of indicating the electrical statte of low voltage transistor` circuits with a neon or glow discharge lamp.

What is claimed is:

1. In combination with a relatively low voltage differential electrical circuit having at least a rst and a second electrical state, load impedance means for said electrical circuit providing a rst voltage during said rst state and a second voltage during said second state, glow discharge means connected with said load impedance means, and means including a direct-current bias supply and alternating current source connected with said glow discharge means providing a predetermined static voltage as low as ten volts and not greatly exceeding twenty volts upon which is superimposed an alternating voltage wave having a peak-to-peak value of a magnitude to render with said first voltage and said static voltage said glow discharge means conductive during said first state and non-conductive during said second state to provide a visual indication ofthe electrical state of said electrical circuit.

2. The combination as dened in claim 1 wherein said glow discharge means is a neon lamp.

3. The combination as defined in claim 2 wherein said electrical circuit comprises a transistor bistable circuit.

4. In combination with an electrical circuit having at least two distinct electrical states, load impedance means providing a voltage variation as said circuit changes from one of said states to the other, said voltage variation being substantially twenty Volts or less, means providing a direct-current bias supply and alternating current supply source providing a predetermined static voltage and alternating voltage, and glow discharge means connected between said output circuit and said direct-current bias supply and alternating current supply source, the voltage variation of said output circuit providing with said direct-current bias supply and alternating current supply source voltage differentials across said lamp of a magnitude to render said lamp conductive during one of said electrical states and non-conductive during the other of states to provide an indication of the electrical state of said circuit.

References Cited in the le of this patent UNITED STATES PATENTS 1,744,840 Strieby et al. Ian. 28, 1930 2,411,848 Camras Dec.'3, 1946 2,644,897 Lo July 7, 1953 2,691,158 Wittenberg Oct. 5, 1954 2,700,750 Dickinson Ian. 25, 1955 2,715,678 Barney Aug. 16, 1955 2,772,410 Logue et al. Nov. 27, 1956 2,776,420 Woll Jan. 1, 1957 OTHER REFERENCES Decade Counter Employs Silicon Transistors, Electronics, Aug. 1955, pages 112-114 by Krenitsky. 

